Conventionally, in order to produce curved surfaces on workpieces, machine tools having a plurality of feed axes are used. When a thin and fragile workpiece, such as turbine blades for steam or gas turbines is processed, it is necessary to prevent deformation of the workpiece due to machining force and vibrations generated from the contact between the tool and the workpiece.
Patent Document 1 describes a method and an apparatus for machining turbine blades. In the invention of Patent Document 1, one end of a workpiece is secured to a fixture and the other end is supported by a center piece of a tail stock. A tension member of the tailstock is engaged with a stepped part of the end of a turbine blade, and axially moved by a hydraulic cylinder, which is provided in the tail stock, in order to apply a tensile force to the turbine blade whereby the turbine blade is processed under the condition that the apparent rigidity of the turbine blade is increased.
In a machine tool for a turbine blade disclosed in Patent Document 2, one end of a turbine blade is secured by a main chuck, and the other end is held by a pressure chuck provided in a sub-chuck head. Compressive force is applied to the turbine blade by pressing the end of the turbine blade with the pressure chuck whereby the turbine blade is processed under the condition that the apparent rigidity of the turbine blade is increased.
Patent Document 1: Japanese Unexamined Patent Publication No. S57-15609
Patent Document 2: Japanese Unexamined Patent Publication No. H10-76437